Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Kendall County, Illinois
EPA puts Kendall County in Zone 1, its highest radon zone, and 35.0% of its 3,045 reported radon tests (2017) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
35.0%
1.3 pts above IL
- Kendall
- 35.0%
- Illinois
- 33.7%
3,045 tests, 2017
Median result
2.8pCi/L
Below action level
- Kendall
- 2.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2017
Tests reported
3,045
13th of 70 by tests
- Kendall
- 3,045
- Cook
- 26,937
Reported to CDC before any fix, 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Illinois
50 of 70
Middle half
- Kendall
- 35.0%
- Stark
- 69.2%
By share, of 70 with 30+ tests
Read a result for Kendall County
Starts at Kendall County's median, 2.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.8 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Kendall County's median reported result, 2017.
The data
Kendall County, At a glance
Kendall County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Kendall County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Kendall County, 2017
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 41.8% |
| 2015 | 42.8% |
| 2016 | 66.7% |
| 2017 | 35.0% |
2017: 35.0%. Across these years the share ran from 35.0% to 66.7%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 3,045 tests reported to CDC for Kendall County over 2017, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).
Kendall County, Compared
Kendall County radon figures, compared
Calculated by Radon411In Kendall County, about 4 in 10 reported tests in 2017 (1,065 of 3,045) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 3.3 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Kendall County runs 1.3 points above its state.
Of 6 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 32.3% (Grundy County) to 45.8% (LaSalle County). By share, Kendall County is 50th of 70 Illinois counties with 30 or more tests for the same period.
Year by year, 2014 opened at 41.8% and 2017 closed at 35.0% (down 6.8 points), with 2016 the high at 66.7%. Half the tests came in under 2.8 pCi/L and half over it; the single highest reached 67.0 pCi/L. Below the action level, 1,107 tests (36.4%) came in under 2 pCi/L, against 37.7% statewide, and 873 tests (28.7%) fell between 2 and 4, against 28.6% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 35.0% share point the same way here. USGS geology rates 100% of the county's land high radon potential.
The busiest year on file was 2014, with 3,603 tests reported; the quietest, 2016, had 36.
Kendall CountyIllinois, pooled
| Year | Tests | Kendall County, at or above 4 pCi/L | Illinois, pooled |
|---|---|---|---|
| 2014 | 3,603 | 41.8% | 37.8% |
| 2015 | 2,262 | 42.8% | 36.6% |
| 2016 | 36 | 66.7% | 17.4% |
| 2017 | 3,045 | 35.0% | 33.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Kendall County, Geology
The ground under Kendall County
PredictedUSGS's geologic map puts all of Kendall County's mapped land in one class: high radon potential. All of it lies in the area the map calls Bloomington Ridged Plain, to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Bloomington Ridged Plain | Wisconsinan glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Kendall County beside the ground around it
Kendall County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 6 counties that border it, none has as large a share of high-potential ground; DeKalb County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Kendall County, Local resources
Radon testing and mitigation in Kendall County
Listed radon businesses with an address in Kendall County:
- IEMA-OHS Radon ProgramIEMA-OHS Radon Program, run by Illinois Emergency Management Agency and Office of Homeland Security, licenses or certifies radon professionals and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Illinois.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Illinois339 professionals are listed in Illinois.
Listed radon professionals by town: Aurora, Joliet, Plainfield, Oswego, Yorkville
What Illinois's program says
- Phone
- (800) 325-1245
- Licensing of radon professionals
The Agency also licenses and regulates the individuals who provide radon measurement and mitigation to the public.
- Disclosure when a home is sold or rented
Illinois Radon Awareness Act - This is the legislation that requires the seller to provide to the buyer of any interest in residential real property the IEMA-OHS pamphlet entitled "Radon Testing Guidelines for Real Estate Transactions" and the Illinois Disclosure of Information on Radon Hazards.
What it means
Kendall County, Questions
Questions about radon in Kendall County
Are radon levels high in Kendall County?
In 2017, 35.0% of the radon tests reported to CDC for Kendall County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.8 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 49 reported a higher share; pooled, the state comes to 33.7%.
Which counties border Kendall County?
Kendall County borders 6 counties: Grundy County, Kane County, DuPage County, DeKalb County, Will County and LaSalle County.
Products
Kendall County, Products
Testing a home in Kendall County
In Kendall County, 35.0% of 3,045 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Kendall County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
Monitor
RadonPro Wi-Fi radon monitor with a built-in Geiger counter
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Kendall County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Kendall County
Explore
Kendall County, Bordering counties
Counties bordering Kendall County
Calculated by Radon411- Radon levels in LaSalle CountyEPA zone 1
45.8%at or above 4 pCi/L
Median 3.6 pCi/L · 1,002 tests · 10.8 points above Kendall County
- Radon levels in DeKalb CountyEPA zone 1
41.1%at or above 4 pCi/L
Median 3.3 pCi/L · 1,707 tests · 6.1 points above Kendall County
- Radon levels in Will CountyEPA zone 2
40.0%at or above 4 pCi/L
Median 3.1 pCi/L · 10,776 tests · 5.0 points above Kendall County
- Radon levels in Kane CountyEPA zone 1
36.6%at or above 4 pCi/L
Median 2.8 pCi/L · 8,682 tests · 1.6 points above Kendall County
- Radon levels in DuPage CountyEPA zone 2
33.7%at or above 4 pCi/L
Median 2.7 pCi/L · 19,401 tests · 1.3 points below Kendall County
- Radon levels in Grundy CountyEPA zone 1
32.3%at or above 4 pCi/L
Median 2.4 pCi/L · 390 tests · 2.7 points below Kendall County
Kendall County, Cities and towns
Cities and towns in Kendall County
Kendall County is growing: the Census Bureau puts it at 145,470 residents on July 1, 2025, up 9.9% from 132,364 in 2020. That works out to 454 people per square mile of land. Aurora, the largest place on its list (181,505 residents in all), extends beyond Kendall County, so no share of the total is worked out for it. Testing is reported here more often than across the state: CDC's 3,045 reported tests for 2017 come to 20.9 for every 1,000 residents (2025 estimate), against 10.9 for Illinois.
From Aurora to Plattville, CDC publishes no figure by town: each reads Kendall County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Auroraextends beyond Kendall County | 181,505 | +0.7% | Counted whole |
| Jolietextends beyond Kendall County | 152,241 | +1.2% | Counted whole |
| Plainfieldextends beyond Kendall County | 50,043 | +11.3% | Counted whole |
| Oswegoextends beyond Kendall County | 39,948 | +15.0% | Counted whole |
| Yorkville | 26,730 | +22.8% | 18.4% |
| Montgomeryextends beyond Kendall County | 21,978 | +7.5% | Counted whole |
| Minookaextends beyond Kendall County | 12,899 | +1.2% | Counted whole |
| Plano | 12,677 | +6.5% | 8.7% |
| Sandwichextends beyond Kendall County | 7,380 | +2.3% | Counted whole |
| Newark | 984 | +0.7% | 0.7% |
| Millingtonextends beyond Kendall County | 629 | +2.1% | Counted whole |
| Millbrook | 291 | +2.5% | 0.2% |
- Lisbon
- Plattville
14 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Kendall County is counted whole, so it has no share.
Kendall County, Homes
Homes in Kendall County
Of Kendall County's 45,775 homes, 74% are detached houses, against 58% across Illinois; 5% are in buildings of five or more homes. Much of Kendall County is recent building: 53% of its homes have gone up since 2000 and the middle year built is 2001, against 1970 for Illinois. Owners live in 84% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.
| Homes | Kendall County | Illinois |
|---|---|---|
| Housing units | 45,775 | 5,443,501 |
| Detached houses | 74% | 58% |
| In buildings of 5 or more | 5% | 22% |
| Mobile homes | under 1% | 2% |
| Built before 1960 | 10% | 38% |
| Built since 2000 | 53% | 16% |
| Middle year built | 2001 | 1970 |
| Owner-occupied | 84% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.